1. Field of the Invention
The present invention relates to a disc brake assembly and disassembly apparatus and, in particular, to a tool for positioning and installing a piston into the piston cylinder of disc brake caliper housing.
2. Prior Art
Disc brake assemblies in automobiles and trucks typically include a rotor disc mounted on the axle of the vehicle and a caliper assembly including one or more hydraulically operated pistons which control the movement of brake pads on each side of the disc causing them to contact the disc and prevent or inhibit the rotation thereof. The caliper typically includes an outer support bracket. After a period of use, parts of the caliper assembly, especially the brake pads and pistons may require replacement. As the brake pads wear due to friction against the disc, they become thinner and the piston assumes an extended position and must be retracted into the piston bore to allow room for new (thicker) pads to replace them. Considerable force may be necessary to retract the pistons into the bore and allow room for the new pads to be mounted.
One of the more common techniques for the retraction of pistons into the bore of a disc brake assembly involves the use of a C-clamp to apply pressure to the piston. The use of a C-clamp (as well as some other tools that have been used for this purpose) often involves difficulty with respect to the alignment of the piston during retraction. The clamp may tend to shift during the procedure, causing the piston to shift from the axial alignment within the piston bore. This may result in the jamming of the piston in the bore or cause damage to the seals and may, as a consequence, require a more complete rebuilding of the assembly.
Various tools and methods have been developed for the retraction of pistons or the installation of new pistons in disc brake assemblies, release of frozen pistons as well as various other problems associated with disc brake assemblies in general and disc brake pistons in particular.
U.S. Pat. No. 3,654,689 to Schwarz discloses a method and apparatus for releasing frozen pistons through the use of an hydraulic system to force the piston(s) against a spacer block. The piston can then be drawn back into the piston bore with the aid of a vacuum line.
U.S. Pat. No. 5,018,261 to Markous and U.S. Pat. No. 5,850,680 to Verrier et al. describes a disc brake assembly tools wherein the piston is forced back into the piston bore by pressure from a threadably adjustable arm positioned in the channel of a caliper body.
It will be appreciated that, although a variety of disc brake caliper tools are known, there is a continuing need for improved tools and methods, especially for use in the retraction of pistons or the installation of new pistons in disc brake assemblies.
It is an object of the present invention to provide a new and improved tool for the retraction of a piston into the piston bore of a disc brake caliper assembly.
It is a further object to provide a piston installation tool for the repair of disc brake caliper assemblies that will exert an even pressure on the edges of a piston and thus maintain the proper axial orientation of the piston during installation.
It is a still further object to provide a disc brake piston installation tool that is easy to use and is powered by pneumatic pressure.
It is a still further object to provide such a tool that may be adapted to fit a variety of disc brake calipers and that may be used to determine the resistance of a piston to retraction.